• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.42-48
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• 1998

Numerical study is presented for the analysis of three-dimensional incompressible turbulent flows in multiblade centrifugal fan. Reynolds-averaged Navier-Stokes equations with standard k - $\epsilon$ turbulence model are transformed to non-orthogonal curvilinear coordinates, and are discretized with finite volume approximations. Linear Upwind Differencing Scheme(LUDS) is used to approximate the convection terms in the governing equations. SIMPLEC algorithm is used as a velocity-pressure correction procedure. The computational area is divided into three blocks; core, impeller and scroll, which are linked by multi-block method. The flow inside of the fan is regarded as steady flow, and mathematical formula established from the cascade theory and empirical coefficient are employed to simulate tile flow through the impeller. From comparisons between the computational results and the experimental data, the validity of the mathematical formula for the blade forces was examined and good results were obtained qualitatively. Hence, we can get the flow characteristics of multi-blade centrifugal fan and it will be a corner stone of the development of the multiblade centrifugal fan.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.10
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• pp.1341-1347
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• 2002

In order to improve efficiency of a system with three-dimensional flow characteristics, this paper presents a new method that overcomes three-dimensional effects by using two-dimensional CFD and neural network. The method was applied to shape optimization of cut-off in a multi-blade fan/scroll system. As the entrance conditions of two-dimensional CFD, the experimental values at the positions out of the inactive zone were used. The distributions of velocity and pressure obtained by two-dimensional CFD were compared with those of three-dimensional CFD and experimental results. It was found that the distributions of velocity and pressure have qualitative similarity. The results of two-dimensional CFD were used for teaming as target values of neural network. The optimal angle and radius of cut-off were determined as 71$^{\circ}$and 0.092 times the outer diameter of impeller, respectively. It is quantified in the previous report that the optimal angle and radius of cut-off are approximately 72$^{\circ}$and 0.08 times the outer diameter of impeller, respectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.225-231
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• 2003

In order to improve efficiency of a system with three-dimensional flow characteristics, this paper presents a new method that overcomes three-dimensional effects by using two-dimensional CFD and response surface method. The method was applied to shape optimization of cut-off in a multi-blade fan/scroll system. As the entrance conditions of two-dimensional CFD, the experimental values at the positions out of the inactive zone were used. In order to examine the validity of the two-dimensional CFD the distributions of velocity and pressure obtained by two-dimensional CFD were compared with those of three-dimensional CFD and experimental results. It was found that the distributions of velocity and pressure show qualitatively similarity. The results of two-dimensional CFD were used for constructing the objective function with design variables using response surface method. The optimal angle and radius of cut-off were determined as $72.4^{\circ}$ and 0.092 times the outer diameter of impeller, respectively. It is quantified the previous report that the optimal angle and radius of cut-off are approximately $72^{\circ}$ and 0.08 times the outer diameter of impeller, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.2
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• pp.167-175
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• 1999

B.P.F.(Blade Passing Frequency) levels were measured with the cut-off clearance changes. The velocity inside the scroll, pressure fluctuation at cut-off region, and the scroll surface pressure distribution along the scroll from the cut-off to outlet were measured. With a certain cut-off clearance the improvement of efficiency and attenuation of B.P.F. noise level could be achieved. The measured results of pressure fluctuation and scroll surface pressure distribution showed that the secondary flow inside the scroll increased B.P.F. noise level at the cut-off region as the cut-off clearance got wide.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.981-982
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• 2012

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1726-1731
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• 2004

This paper presents the response surface optimization method using three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved blades centrifugal fan. For numerical analysis, Reynolds-averaged Navier-Stokes equations with $k-{\varepsilon}$ turbulence model are discretized with finite volume approximations. In order to reduce huge computing time due to a large number of blades in forward-curved blades centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models. Three geometric variables, i.e., location of cut off, radius of cut off, and width of impeller, and one operating variable, i.e., flow rate, were selected as design variables. As a main result of the optimization, the efficiency was successfully improved. And, optimum design flow rate was found by using flow rate as one of design variables. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1332-1338
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• 2004

This paper presents the response surface optimization method using three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved blades centrifugal fan. For numerical analysis, Reynolds-averaged Navier-Stokes equations with k-$\varepsilon$ turbulence model are discretized with finite volume approximations. In order to reduce huge computing time due to a large number of blades in forward-curved blades centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models. Three geometric variables, i.e., location of cut off, radius of cut off, and width of impeller, and one operating variable, i.e., flow rate, were selected as design variables. As a main result of the optimization, the efficiency was successfully improved. And, optimum design flow rate was found by using flow rate as one of design variables. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.227-233
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• 2002

It is common for highly loaded supersonic stage to have very high relative inlet Mach number. To get this level of inlet Mach number, rotor blade outer diameter or rotational speed should be increased. In the case of commercial turbo-fan engine, it is preferred to make the rotor blade outer diameter large than increasing the rotational speed. But, for multi-stage fan of military engines, overall diameter is often restricted and they are apt to increase the rotational speed. With high rotational speed, relative inlet Mach number is likely to be well supersonic over the entire rotor blade span and the characteristic of the stage is affected with meridional shape of the stage, especially at near hub or tip. In this paper, the aerodynamic performance of two different hub surface shape is compared and it's merit and demerits were discussed.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.137-142
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• 2000

The turbulent broadband sound power from a forward curved bladed fan can be modeled by the trailing edge noise. The trailing edge noise is usually influenced by inflow turbulence, separation, and boundary layer on the blade. This paper reports the effects of the solidity (C/s) and the stagger angles upon the trailing edge noise with respect to the trailing edge shapes of circular-arc cambered blade of multi-bladed fan, and discusses the major physical mechanism of reduced noise lot the circular trailing-edged case.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.80-85
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• 2014

High-volume low-speed (HVLS) fans are one category of ceiling fan installed in large enclosings such as warehouses, large barns and health clubs in order to generate comfortable air circulation. As a rotary blade, aerodynamic performance of a HVLS fan is predominantly related to its airfoil(s), and the pitch and twist angles. This paper first, investigates the effects of airfoil on the performances of three different HVLS fans with NACA 5414, 6413 and 7415 airfoils. The fans have six untwisted blades with the diameter of 6 m and rotate at 60 RPM. The blades pitch angels are $12^{\circ}$, $12^{\circ}$ and $13^{\circ}$, respectively. The results are presented in the form of the aerodynamic forces and moments, volumetric flow rate and streamlines. Regarding the volumetric flow of air, the results show that the model with NACA 7415 has the best performance. Hence, two other HVLS fans with the same airfoil but, with four and five blades are studied in order to investigate the effects of number of blades. From the point of view of air circulation still the six-bladed fan is the best one; however, the five-bladed fan is more efficient in power consumption.